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fix: target-size compression now respects the target

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The binary search found the right quality but sharp(buffer).toBuffer()
re-encoded at default quality 80, inflating the output (e.g. 50KB target
producing 90KB). Replaced buffer-wrapping with proper Sharp pipelines
that include .toFormat() with the proven quality. Also added progressive
dimension reduction when quality alone cannot reach the target, and
tightened tolerance to only accept at-or-below-target results.
This commit is contained in:
SnapOtter
2026-05-11 16:19:40 +08:00
parent 69597f3c39
commit e6a35265ef
3 changed files with 233 additions and 37 deletions
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packages/image-engine/src/operations/compress.ts
+60 -29
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@@ -49,44 +49,75 @@ export async function compress(image: Sharp, options: CompressOptions): Promise<
return image.toFormat(outputFormat, formatOpts(outputFormat, q));
}
async function findBestQuality(
inputBuffer: Buffer,
resize: { width: number; height: number } | null,
format: keyof import("sharp").FormatEnum,
targetBytes: number,
): Promise<number | null> {
let low = 1;
let high = 100;
let bestQuality: number | null = null;
const maxIterations = 8;
const tolerance = 0.05;
for (let i = 0; i < maxIterations && low <= high; i++) {
const mid = Math.min(100, Math.max(1, Math.round((low + high) / 2)));
let pipeline = sharp(inputBuffer);
if (resize) pipeline = pipeline.resize(resize.width, resize.height);
const resultBuffer = await pipeline.toFormat(format, formatOpts(format, mid)).toBuffer();
const resultSize = resultBuffer.length;
if (resultSize <= targetBytes) {
bestQuality = mid;
if ((targetBytes - resultSize) / targetBytes <= tolerance) break;
low = mid + 1;
} else {
high = mid - 1;
}
}
return bestQuality;
}
async function compressToTargetSize(
inputBuffer: Buffer,
format: keyof import("sharp").FormatEnum,
targetBytes: number,
): Promise<Sharp> {
let low = 1;
let high = 100;
let bestQuality = 1;
let bestBuffer: Buffer | null = null;
const maxIterations = 8;
const tolerance = 0.05; // 5%
const quality = await findBestQuality(inputBuffer, null, format, targetBytes);
if (quality !== null) {
return sharp(inputBuffer).toFormat(format, formatOpts(format, quality));
}
for (let i = 0; i < maxIterations && low <= high; i++) {
const mid = Math.min(100, Math.max(1, Math.round((low + high) / 2)));
const attempt = sharp(inputBuffer).toFormat(format, formatOpts(format, mid));
const resultBuffer = await attempt.toBuffer();
const resultSize = resultBuffer.length;
const metadata = await sharp(inputBuffer).metadata();
const originalWidth = metadata.width ?? 0;
const originalHeight = metadata.height ?? 0;
if (Math.abs(resultSize - targetBytes) / targetBytes <= tolerance) {
bestQuality = mid;
bestBuffer = resultBuffer;
break;
}
if (originalWidth === 0 || originalHeight === 0) {
return sharp(inputBuffer).toFormat(format, formatOpts(format, 1));
}
if (resultSize > targetBytes) {
high = mid - 1;
} else {
low = mid + 1;
bestQuality = mid;
bestBuffer = resultBuffer;
const scaleFactor = 0.75;
const maxScalePasses = 8;
let lastWidth = originalWidth;
let lastHeight = originalHeight;
for (let pass = 1; pass <= maxScalePasses; pass++) {
const factor = scaleFactor ** pass;
const newWidth = Math.round(originalWidth * factor);
const newHeight = Math.round(originalHeight * factor);
if (newWidth < 10 || newHeight < 10) break;
lastWidth = newWidth;
lastHeight = newHeight;
const dims = { width: newWidth, height: newHeight };
const q = await findBestQuality(inputBuffer, dims, format, targetBytes);
if (q !== null) {
return sharp(inputBuffer).resize(newWidth, newHeight).toFormat(format, formatOpts(format, q));
}
}
if (bestBuffer === null) {
bestBuffer = await sharp(inputBuffer)
.toFormat(format, formatOpts(format, bestQuality))
.toBuffer();
}
return sharp(bestBuffer);
return sharp(inputBuffer).resize(lastWidth, lastHeight).toFormat(format, formatOpts(format, 1));
}